Selling a product without proper installation

On Air TV called me to sell me the new DSTV explorer package for R149 a month with installation included. Now once I have received the package and contact the installer, I am told that the 2 points I currently have in my house will no longer work, just the one because the installation voucher I got is wrong. How can you sell me something when you fully know that my current setup allows for 2 TVs and now I`m limited to 1? The voucher CLEARLY states 75m cable and dish included, I have all the equipment already, the installer will use my existing equipment BUT STILL cannot do extra view???? Please Fix ASAP!!!!